Most studies on the economic benefits of GMO crops are focused on farms that grow GMO crops. A new study from the University of Minnesota finds that there are economic benefits for those who choose to grow non-gmo crops as well. This is based on 45 years of data on pests in the corn growing areas of Illinois, Minnesota, Wisconsin, Iowa and Nebraska. The European corn borer which is the most common threat to crops here cannot distinguish between Bt corn and non Bt corn so it lays eggs in both types of crops: in the bt corn plants as well as the non-bt refuge plants. Since the pests cannot survive in the fields growing bt corn, the threat to the non-bt fields is also diminished.
This process is reflected in remarkable numbers: over 14 years, the benefit from growing bt corn in Illinois, Minnesota and Wisconsin was $3.2 bn, but even the non-bt corn growers benefited from lower crop loss to the extent of $2.4 bn. There could possibly be gains for produce as well which benefits from suppression of the European corn borer but this is not documented yet. Here is the original paper.